There' s no need to buy anything for it just yet... best thing to do is come down to the club and see what setups & extras the more experienced drivers are running, I'm more than happy to help with that I'm there most weeks and ran a B4 plenty there
The only things you might find is the standard steel turnbuckles tend to bend quite easily in crashes so most upgrade to the factoryteam titanium versions.
The standard driveshaft dogbones tend to pop out sometimes aswell so getting the cvd driveshafts will elimate that problem if you come across it.
Anything else like factoryteam shocks are just for ease of setups & you don't need any of the alloy bits unless your having alot of breakages or like to be pimp
As said above the electronics make the most significant difference when upgrading bits like a faster servo & more powerfull speed controller & motor.